Dual-curing coating compositions

ABSTRACT

The present invention relates to polymerizable compositions which contain components that can be crosslinked both via isocyanurate bonds and by a radical reaction mechanism. The invention further relates to methods by way of which polymers can be produced from said compositions.

The present invention relates to polymerizable compositions comprisingcomponents which can be crosslinked either via isocyanurate bonds or bya free-radical reaction mechanism. It further describes processes bywhich polymers can be prepared from these compositions.

WO 2015/155195 describes a composite material obtainable from areinforcing material and a polyurethane composition consisting of atleast one polyisocyanate (PIC), a PIC-reactive component consisting ofat least one polyol and at least one methacrylate having OH groups, anda free-radical initiator. The addition reaction between PIC and OHgroups takes place simultaneously with the free-radically initiatedchain polymerization of the methacrylates. A disadvantage of the processused, in addition to the short pot lives/gel times of the polyurethanecompositions, is the fact that, in the preparation of polyurethanes, themixing ratio of the components, especially of the polyisocyanate and thepolyol, is limited by the necessity of keeping the molar ratio ofisocyanate and isocyanate-reactive groups close to 1:1.

WO 2016/087366 describes a free-radically polymerizable compositionconsisting of a polyurethane containing double bonds and a reactivediluent based on various methacrylates.

A disadvantage here is the two-stage reaction regime (the reaction ofthe hydroxymethacrylate with an isocyanate takes place in the firststage, and the reaction of the isocyanate-bonded (meth)acrylates to givepolyacrylates takes place in the second stage, in order to obtain acrosslinked composition). A further disadvantage is the necessity ofworking under precise stoichiometric conditions in order to avoid freeunconverted isocyanate.

U.S. Pat No. 6,133,397 and PCT/EP2017/073276 describe coatingcompositions that are cured primarily through the crosslinking ofisocyanate groups with one another. This forms isocyanurate groups interalia that impart advantageous properties to the coatings formed.

The low-monomer polyisocyanate compositions described as reactants inthese applications have a relatively high viscosity which can be ahindrance in some applications.

The addition of monomeric polyisocyanates as reactive diluents isundesirable for reasons of occupational hygiene in many cases sincethese compounds are firstly volatile, and secondly act as irritants.Alternatively, conventional organic solvents can be used to reduce theviscosity. However, these are disadvantageous for reasons ofenvironmental protection since they are released into the environmentduring or after the polymerization.

At the same time, it is desirable for coating applications when theviscosity of the coating composition even immediately before applicationcan be increased to such an extent that running of the coating off anoblique surface is avoided. Since the crosslinking reaction ofisocyanate groups, for example to give isocyanurate groups, generallytakes at least a few minutes, the compositions described in U.S. Pat.No. 6,133,397 do not meet this requirement.

What are desirable, therefore, are compositions having a viscosity inthe unprocessed state, without use of organic solvents, that can beadjusted with maximum freedom according to the demands of the respectiveapplication, and the viscosity of which can be increased with maximumspeed after application to a surface. To the extent that such coatingsare used for production of coatings, the coatings formed are also tohave good optical properties, especially clarity.

This object is achieved by the embodiments of the invention disclosed inthe claims and in the description below.

In a first embodiment, the present invention relates to a coatingcomposition having a ratio of isocyanate groups to isocyanate-reactivegroups of at least 2.0:1.0, comprising:

-   -   a) an isocyanate component A;    -   b) at least one trimerization catalyst C; and    -   c) at least one component selected from the group consisting of        components B, D and E, where    -   component B has at least one ethylenic double bond but no        isocyanate-reactive group;    -   component D has at least one isocyanate-reactive group and at        least one ethylenic double bond in one molecule; and    -   component E has both at least one isocyanate group and at least        one ethylenic double bond in one molecule.

The isocyanate component A enables the formation of a polymer that formsthrough the addition of isocyanate groups. This forms isocyanurategroups in particular. The crosslinking of the isocyanate groups presentin the isocyanate component A endows the polymer with the majority ofits mechanical and chemical stability. The crosslinking of theisocyanate groups is mediated by the trimerization catalyst C.

Components B, D and E are each characterized by the presence of anethylenic double bond. This double bond is a prerequisite for a secondcrosslinking mechanism to be available in addition to the polyadditionof the isocyanate groups in the polymerizable composition. Each of thesecomponents enables crosslinking by free-radical polymerization. This isa crosslinking mechanism that enables the buildup of viscosity within aperiod of a few seconds. The use of these individual components orparticular combinations of components has specific advantages here:

Component B lowers the viscosity of the polymerizable composition andcan be rapidly crosslinked by free-radical polymerization and thus usedfor rapid buildup of viscosity. If there is just a component B presentin the polymerizable composition without components D or E, the twodifferent crosslinking mechanisms give rise to two different polymernetworks. This can lead to turbidity in the finished product and undersome circumstances to poorer mechanical properties.

In areas of application where this is to be avoided, component B is usedin combination with a component D or E. It can also be used incombination with both components. Components D and E mediate thecrosslinking of the network, formed by free-radical polymerization, ofcomponent B with the polymer of isocyanate component A formed throughpolyaddition of the isocyanate groups. They thus ensure that there areno two separate polymer networks of components A and B present in thepolymer, but rather a single polymer network.

Even if they are used without an additional component B, components Dand E enable the formation of a polymer network via free-radicalpolymerization. Similarly to the case of exclusive use of component B,rapid buildup of viscosity after application of the composition of theinvention is enabled. However, unlike component B, components D and Eare only of limited suitability as reactive diluents.

In a preferred embodiment of the present invention, the polymerizablecomposition contains at least one of the two components D and E, but nocomponent B.

In another preferred embodiment, the composition of the inventioncontains a component B and at least one of the two components D and E.Particular preference is given to the combination of B and D.

In a preferred embodiment, the proportions of components B, D and E areadjusted such that the coating composition, after the free-radicalpolymerization of the ethylenic double bonds, does not run on a verticalsurface within a period of at least 30 seconds, preferably at least 2minutes and more preferably at least 10 minutes. A coating compositiondoes not run if no difference in the coating thickness is visuallyperceptible between the upper end of the surface and the lower endthereof after the aforementioned time.

Whether a coating composition fulfils this criterion can be determinedby simple preliminary tests. The composition is applied to a surface andtreated with actinic radiation so as to initiate free-radicalpolymerization. Subsequently, the surface is stored vertically at 23° C.(room temperature) for the abovementioned period and then visuallyassessed.

Dimensional stability of a coating results from the interplay betweencoating thickness and viscosity. The higher the coating thickness, thehigher the viscosity of the coating has to be.

In a particular embodiment of the invention, target coating thicknessesare at least 0.005 mm, preferably at least 0.02 mm and most preferablyat least 0.04 mm, and at most 5 mm, preferably at most 0.5 mm and mostpreferably at most 0.1 mm.

In a further preferred embodiment, the proportion of components B, D andE in the composition of the invention is such that the viscosity of thecoating is at least doubled, preferably quadrupled and more preferablydectupled after polymerization triggered by actinic radiation.

In a further preferred embodiment, the dynamic viscosity to EN ISO2884-1:2006 measured in a cone-plate viscometer at room temperatureafter polymerization with actinic radiation is at least 200 mPas,preferably at least 500 mPas, more preferably at least 1000 mPas, evenmore preferably at least 10 000 mPas and even more preferably still atleast 100 000 mPas.

In a preferred embodiment, the polymerizable composition of theinvention comprises isocyanate component A and component B preferably ina quantitative ratio that lowers the viscosity of the undilutedisocyanate component to at most 75%, preferably at most 25%, morepreferably at most 5% and most preferably to at most 1% of the viscosityof undiluted isocyanate component A. The presence of at least one ofcomponents D and E is particularly preferred in this embodiment.

In a preferred embodiment, the quantitative ratio of component A to thetotal amount of components B, D and E is such that the polymerizablecomposition before each crosslinking has a viscosity at room temperatureof at most 100 000 mPas, more preferably of at most 10 000 mPas, evenmore preferably of at most 1000 mPas and most preferably at most 100mPas.

The polymer obtainable by polymerizing the coating composition of theinvention receives its advantageous properties very substantiallythrough crosslinking of the isocyanate groups with one another.Consequently, it is essential to the invention that the ratio ofisocyanate groups to the total amount of the isocyanate-reactive groupsin the polymerizable composition is restricted such that there is adistinct molar excess of isocyanate groups. The molar ratio ofisocyanate groups of the isocyanate component to isocyanate-reactivegroups in the reactive resin is consequently at least 2.0:1.0,preferably at least 3.0:1.0, more preferably at least 4.0:1.0 and evenmore preferably at least 8.0:1,0. “Isocyanate-reactive groups” in thecontext of the present application are hydroxyl, thiol, carboxyl andamino groups, amides, urethanes, acid anhydrides and epoxides. Theisocyanate groups present in the polymerizable composition are presentin components A and—if present—E. The isocyanate-reactive groups may inprinciple be present in all other components except for component B.

By comparison with the polyurethane resins known from WO 2015/155195with additional radiative curing, the use of the polymerizablecomposition of the invention enables greater flexibility in theselection of the proportions of the individual components. If apolyurethane or a polyurea is to be obtained, the molar ratio ofisocyanate groups to isocyanate-reactive groups must if possible beclose to 1:1. According to the present invention, however, there is adistinct excess of isocyanate groups that is consequently not justacceptable but actually desired because the polymer formed owes itsadvantageous properties very substantially to the reaction of isocyanategroups with other isocyanate groups. The structures thus formed,especially the isocyanurate groups, lead to polymers with exceptionalhardness and exceptional stability to chemicals.

Isocyanate Component A

“Isocyanate component A” in the context of the invention refers to theisocyanate component in the starting reaction mixture. In other words,this is the sum total of all the compounds in the starting reactionmixture that have isocyanate groups, except for component E. Theisocyanate component A is thus used as reactant in the process of theinvention. When reference is made here to “isocyanate component A”,especially to “providing the isocyanate component A”, this means thatthe isocyanate component A exists and is used as reactant. Theisocyanate component A preferably contains at least one polyisocyanate.

The term “polyisocyanate” as used here is a collective term forcompounds containing two or more isocyanate groups in the molecule (thisis understood by the person skilled in the art to mean free isocyanategroups of the general structure —N═C═O). The simplest and most importantrepresentatives of these polyisocyanates are the diisocyanates. Thesehave the general structure O═C═N—R—N═C═O where R typically representsaliphatic, alicyclic and/or aromatic radicals.

Because of the polyfunctionality (≥2 isocyanate groups), it is possibleto use polyisocyanates to produce a multitude of polymers (e.g.polyurethanes, polyureas and polyisocyanurates) and low molecular weightcompounds (for example those having uretdione, isocyanurate,allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrionestructure).

The term “polyisocyanates” in this application refers equally tomonomeric and/or oligomeric polyisocyanates. For the understanding ofmany aspects of the invention, however, it is important to distinguishbetween monomeric diisocyanates and oligomeric polyisocyanates. Wherereference is made in this application to “oligomeric polyisocyanates”,this means polyisocyanates formed from at least two monomericdiisocyanate molecules, i.e. compounds that constitute or contain areaction product formed from at least two monomeric diisocyanatemolecules.

The preparation of oligomeric polyisocyanates from monomericdiisocyanates is also referred to here as modification of monomericdiisocyanates. This “modification” as used here means the reaction ofmonomeric diisocyanates to give oligomeric polyisocyanates havinguretdione, isocyanurate, allophanate, biuret, iminooxadiazinedioneand/or oxadiazinetrione structure.

For example, hexamethylene diisocyanate (HDI) is a “monomericdiisocyanate” since it contains two isocyanate groups and is not areaction product of at least two polyisocyanate molecules:

Reaction products which are formed from at least two HDI molecules andstill have at least two isocyanate groups, by contrast, are “oligomericpolyisocyanates” within the context of the invention. Representatives ofsuch “oligomeric polyisocyanates” are, proceeding from monomeric HDI,for example, HDI isocyanurate and HDI biuret, each of which is formedfrom three monomeric HDI units:

According to the invention, the proportion by weight of isocyanategroups based on the total amount of the isocyanate component A is atleast 15% by weight.

In principle, monomeric and oligomeric polyisocyanates are equallysuitable for use in the isocyanate component A of the invention.Consequently, the isocyanate component A may consist essentially ofmonomeric polyisocyanates or essentially of oligomeric polyisocyanates.It may alternatively comprise oligomeric and monomeric polyisocyanatesin any desired mixing ratios.

In a preferred embodiment of the invention, the isocyanate component Aused as reactant in the trimerization has a low level of monomers (i.e.a low level of monomeric diisocyanates) and already contains oligomericpolyisocyanates. The expressions “having a low level of monomers” and“having a low level of monomeric diisocyanates” are used heresynonymously in relation to the isocyanate component A.

Results of particular practical relevance are established when theisocyanate component A has a proportion of monomeric diisocyanates inthe isocyanate component A of not more than 20% by weight, especiallynot more than 15% by weight or not more than 10% by weight, based ineach case on the weight of the isocyanate component A. Preferably, theisocyanate component A has a content of monomeric diisocyanates of notmore than 5% by weight, preferably not more than 2.0% by weight, morepreferably not more than 1.0% by weight, based in each case on theweight of the isocyanate component A. Particularly good results areestablished when the isocyanate component A is essentially free ofmonomeric diisocyanates. “Essentially free” here means that the contentof monomeric diisocyanates is not more than 0.5% by weight, based on theweight of the isocyanate component A.

In a particularly preferred embodiment of the invention, the isocyanatecomponent A consists entirely or to an extent of at least 80%, 85%, 90%,95%, 98%, 99% or 99.5% by weight, based in each case on the weight ofthe isocyanate component A, of oligomeric polyisocyanates. Preference isgiven here to a content of oligomeric polyisocyanates of at least 99% byweight. This content of oligomeric polyisocyanates relates to theisocyanate component A as provided. In other words, the oligomericpolyisocyanates are not formed as intermediate during the process of theinvention, but are already present in the isocyanate component A used asreactant on commencement of the reaction.

Polyisocyanate compositions which have a low level of monomers or areessentially free of monomeric isocyanates can be obtained by conducting,after the actual modification reaction, in each case, at least onefurther process step for removal of the unconverted excess monomericdiisocyanates. This removal of monomers can be effected in aparticularly practical manner by processes known per se, preferably bythin-film distillation under high vacuum or by extraction with suitablesolvents that are inert toward isocyanate groups, for example aliphaticor cycloaliphatic hydrocarbons such as pentane, hexane, heptane,cyclopentane or cyclohexane.

In a preferred embodiment of the invention, the isocyanate component Aof the invention is obtained by modifying monomeric diisocyanates withsubsequent removal of unconverted monomers.

In a particular embodiment of the invention, an isocyanate component Ahaving a low level of monomers, however, contains an extra monomericdiisocyanate. In this context, “extra monomeric diisocyanate” means thatit differs from the monomeric diisocyanates which have been used forpreparation of the oligomeric polyisocyanates present in the isocyanatecomponent A.

An addition of extra monomeric diisocyanate may be advantageous forachievement of special technical effects, for example an exceptionalhardness. Results of particular practical relevance are established whenthe isocyanate component A has a proportion of extra monomericdiisocyanate in the isocyanate component A of not more than 20% byweight, especially not more than 15% by weight or not more than 10% byweight, based in each case on the weight of the isocyanate component A.Preferably, the isocyanate component A has a content of extra monomericdiisocyanate of not more than 5% by weight, especially not more than2.0% by weight, more preferably not more than 1.0% by weight, based ineach case on the weight of the isocyanate component A.

In a further particular embodiment of the process of the invention, theisocyanate component A contains monomeric monoisocyanates or monomericisocyanates having an isocyanate functionality greater than two, i.e.having more than two isocyanate groups per molecule. The addition ofmonomeric monoisocyanates or monomeric isocyanates having an isocyanatefunctionality greater than two has been found to be advantageous inorder to influence the network density of the coating. Results ofparticular practical relevance are established when the isocyanatecomponent A has a proportion of monomeric monoisocyanates or monomericisocyanates having an isocyanate functionality greater than two in theisocyanate component A of not more than 20% by weight, especially notmore than 15% by weight or not more than 10% by weight, based in eachcase on the weight of the isocyanate component A. Preferably, theisocyanate component A has a content of monomeric monoisocyanates ormonomeric isocyanates having an isocyanate functionality greater thantwo of not more than 5% by weight, preferably not more than 2.0% byweight, more preferably not more than 1.0% by weight, based in each caseon the weight of the isocyanate component A. Preferably, no monomericmonoisocyanate or monomeric isocyanate having an isocyanatefunctionality greater than two is used in the trimerization reaction ofthe invention.

The oligomeric polyisocyanates may, in accordance with the invention,especially have uretdione, isocyanurate, allophanate, biuret,iminooxadiazinedione and/or oxadiazinetrione structure. In oneembodiment of the invention, the oligomeric polyisocyanates have atleast one of the following oligomeric structure types or mixturesthereof:

In a preferred embodiment of the invention, an isocyanate component A isused, wherein the isocyanurate structure component is at least 50 mol %,preferably at least 60 mol %, more preferably at least 70 mol %, evenmore preferably at least 80 mol %, even more preferably still at least90 mol % and especially preferably at least 95 mol %, based on the sumtotal of the oligomeric structures from the group consisting ofuretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione andoxadiazinetrione structure present in the isocyanate component A, isused.

In a further preferred embodiment of the invention, in the process ofthe invention, an isocyanate component A containing, as well as theisocyanurate structure, at least one further oligomeric polyisocyanatehaving uretdione, biuret, allophanate, iminooxadiazinedione andoxadiazinetrione structure and mixtures thereof is used.

The proportions of uretdione, isocyanurate, allophanate, biuret,iminooxadiazinedione and/or oxadiazinetrione structure in the isocyanatecomponent A can be determined, for example, by NMR spectroscopy. It ispossible here with preference to use 13C NMR spectroscopy, preferably inproton-decoupled form, since the oligomeric structures mentioned givecharacteristic signals.

Irrespective of the underlying oligomeric structure (uretdione,isocyanurate, allophanate, biuret, iminooxadiazinedione and/oroxadiazinetrione structure), an oligomeric isocyanate component A foruse in the process of the invention and/or the oligomericpolyisocyanates present therein preferably have/has an (average) NCOfunctionality of 2.0 to 5.0, preferably of 2.3 to 4.5.

Results of particular practical relevance are established when theisocyanate component A to be used in accordance with the invention has acontent of isocyanate groups of 8.0% to 28.0% by weight, preferably of14.0% to 25.0% by weight, based in each case on the weight of theisocyanate component A.

Preparation processes for the oligomeric polyisocyanates havinguretdione, isocyanurate, allophanate, biuret, iminooxadiazinedioneand/or oxadiazinetrione structure that are to be used in accordance withthe invention in the isocyanate component A are described, for example,in J. Prakt. Chem. 336 (1994) 185-200, in DE-A 1 670 666, DE-A 1 954093, DE-A 2 414 413, DE-A 2 452 532, DE-A 2 641 380, DE-A 3 700 209,DE-A 3 900 053 and DE-A 3 928 503 or in EP-A 0 336 205, EP-A 0 339 396and EP-A 0 798 299.

In an additional or alternative embodiment of the invention, theisocyanate component A of the invention is defined in that it containsoligomeric polyisocyanates which have been obtained from monomericdiisocyanates, irrespective of the nature of the modification reactionused, with observation of an oligomerization level of 5% to 45%,preferably 10% to 40%, more preferably 15% to 30%. “Oligomerizationlevel” is understood here to mean the percentage of isocyanate groupsoriginally present in the starting mixture which are consumed during thepreparation process to form uretdione, isocyanurate, allophanate,biuret, iminooxadiazinedione and/or oxadiazinetrione structures.

Suitable polyisocyanates for production of the isocyanate component Afor use in the process of the invention and the monomeric and/oroligomeric polyisocyanates present therein are any desiredpolyisocyanates obtainable in various ways, for example by phosgenationin the liquid or gas phase or by a phosgene-free route, for example bythermal urethane cleavage. Particularly good results are establishedwhen the polyisocyanates are monomeric diisocyanates. Preferredmonomeric diisocyanates are those having a molecular weight in the rangefrom 140 to 400 g/mol, having aliphatically, cycloaliphaticaily,araliphatically and/or aromatically bonded isocyanate groups, forexample 1,4-diisocyanatobutane (BDI), 1,5-diisocyanatopentane (PDI),1,6-diisocyanatohexane (HDI), 2-methyl-1,5-diisocyanatopentane,1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3-and 1,4-diisocyanatocyclohexane,1,4-diisocyanato-3,3,5-trimethylcyclohexane,1,3-diisocyanato-2-methylcyclohexane,1,3-diisocyanato-4-methylcyclohexane,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate; IPDI),1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, 2,4′- and4,4′-diisocyanatodicyclohexylmethane (H12MDI), 1,3- and1,4-bis(isocyanatomethyl)cyclohexane, bis(isocyanatomethyl)norbornane(NBDI), 4,4′-diisocyanato-3,3′-dimethyldicyclohexyl methane,4,4′-diisocyanato-3,3′,5,5′-tetramethyldicyclohexylmethane,4,4′-diisocyanato-1,1′-bi(cyclohexyl),4,4′-diisocyanato-3,3′-dimethyl-1,1′-bi(cyclohexyl),4,4′-diisocyanato-2,2′,5,5′-tetramethyl-1,1′-bi(cyclohexyl),1,8-diisocyanato-p-menthane, 1,3-diisocyanatoadamantane,1,3-dimethyl-5,7-diisocyanatoadamantane, 1,3- and1,4-bis(isocyanatomethyl)benzene (xylylene diisocyanate; XDI), 1,3- and1,4-bis(1-isocyanato-1-methylethyl)benzene (TMXDI) andbis(4-(1-isocyanato-1-methylethyl)phenyl) carbonate, 2,4- and2,6-diisocyanatotoluene (TDI), 2,4′- and4,4′-diisocyanatodiphenylmethane (MDI), 1,5-diisocyanatonaphthalene andany desired mixtures of such diisocyanates. Further diisocyanates thatare likewise suitable can additionally be found, for example, in JustusLiebigs Annalen der Chemie, volume 562 (1949) p. 75-136.

Suitable monomeric monoisocyanates which can optionally be used in theisocyanate component A are, for example, n-butyl isocyanate, n-amylisocyanate, n-hexyl isocyanate, n-heptyl isocyanate, n-octyl isocyanate,undecyl isocyanate, dodecyl isocyanate, tetradecyl isocyanate, cetylisocyanate, stearyl isocyanate, cyclopentyl isocyanate, cyclohexylisocyanate, 3- or 4-methylcyclohexyl isocyanate or any desired mixturesof such monoisocyanates. An example of a monomeric isocyanate having anisocyanate functionality greater than two which can optionally be addedto the isocyanate component A is 4-isocyanatomethyloctane1,8-diisocyanate (triisocyanatononane; TIN).

In one embodiment of the invention, the isocyanate component A containsnot more than 30% by weight, especially not more than 20% by weight, notmore than 15% by weight, not more than 10% by weight, not more than 5%by weight or not more than 1% by weight, based in each case on theweight of the isocyanate component A, of aromatic polyisocyanates. Asused here, “aromatic polyisocyanate” means a polyisocyanate having atleast one aromatically bonded isocyanate group.

Aromatically bonded isocyanate groups are understood to mean isocyanategroups bonded to an aromatic hydrocarbyl radical.

In a preferred embodiment of the process of the invention, an isocyanatecomponent A having exclusively aliphatically and/or cycloaliphaticallybonded isocyanate groups is used.

Aliphatically and cycloaliphatically bonded isocyanate groups areunderstood to mean isocyanate groups bonded, respectively, to analiphatic and cycloaliphatic hydrocarbyl radical.

In another preferred embodiment of the process of the invention, anisocyanate component A consisting of or comprising one or moreoligomeric polyisocyanates is used, where the one or more oligomericpolyisocyanates has/have exclusively aliphatically and/orcycloaliphatically bonded isocyanate groups.

In a further embodiment of the invention, the isocyanate component Aconsists to an extent of at least 70%, 80%, 85%, 90%, 95%, 98% or 99% byweight, based in each case on the weight of the isocyanate component A,of polyisocyanates having exclusively aliphatically and/orcycloaliphatically bonded isocyanate groups. Practical experiments haveshown that particularly good results can be achieved with isocyanatecomponent A in which the oligomeric polyisocyanates present therein haveexclusively aliphatically and/or cycloaliphatically bonded isocyanategroups.

In a particularly preferred embodiment of the process of the invention,a polyisocyanate composition A is used which consists of or comprisesone or more oligomeric polyisocyanates, where the one or more oligomericpolyisocyanates is/are based on 1,4-diisocyanatobutane (BDI),1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI), isophoronediisocyanate (IPDI) or 4,4′-diisocyanatodicyclohexylmethane (H12MDI) ormixtures thereof.

In a further embodiment of the invention, in the process of theinvention, isocyanate components A having a viscosity greater than 500mPas and less than 200 000 mPas, preferably greater than 1000 mPas andless than 100 000 mPas, more preferably greater than 1000 mPas and lessthan 50 000 mPas and even more preferably greater than 1000 mPas andless than 25 000 mPas, measured according to DIN EN ISO 3219 at 21° C.,are used.

Component B

Suitable components B are all compounds containing at least oneethylenic double bond. This ethylenic double bond is crosslinkable withother ethylenic double bonds by a free-radical reaction mechanism. Thiscondition is met by preferably activated double bonds between the αcarbon atom and the β carbon atom alongside an activating group. Theactivating group is preferably a carboxyl or carbonyl group. Mostpreferably, component B is an acrylate, a methacrylate, the ester of anacrylate or the ester of a methacrylate. Preferably, component B doesnot contain any of the isocyanate-reactive groups as defined further upin this application or any isocyanate group either.

Preferred components B are components B1 with one, component B2 with twoand component B3 with three of the above-described ethylenic doublebonds. Particular preference is given to B1 and/or B2.

In a preferred embodiment, component B used is a mixture of at least onecomponent B1 and at least one component B2.

In a further preferred embodiment, component B used is a mixture of atleast one component B1 and at least one component B3.

In yet a further preferred embodiment, component B used is a mixture ofat least one component B2 and at least one component B3.

In yet a further preferred embodiment, component B used is a mixture ofat least one component B1, at least one component B2 and at least onecomponent B3. Preference is given to using a mixture of at least onecomponent B1 with at least one component B2. The mass ratio ofcomponents B1 and B2 here is preferably between 30:1 and 1:30, morepreferably between 20:1 and 1:20, even more preferably between 1:10 and10:1 and most preferably between 2:1 and 1:2.

Preferred components B1 are methyl (meth)acrylate, ethyl (meth)acrylate,propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate,isobutyl (meth)acrylate, tert-butyl (meth)acrylate, hexyl(meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,cyclohexyl (meth)acrylate, octyl (meth)acrylate, isooctyl(meth)acrylate, decyl (meth)acrylate, benzyl (meth)acrylate,tetrahydrofurfuryl (meth)acrylate, octadecyl (meth)acrylate, dodecyl(meth)acrylate, tetradecyl (meth)acrylate, oleyl (meth)acrylate,4-methylphenyl (meth)acrylate, benzyl (meth)acrylate, furfuryl(meth)acrylate, cetyl (meth)acrylate, 2-phenylethyl (meth)acrylate,isobornyl (meth)acrylate, neopentyl (meth)acrylate, methacrylamide andn-isopropylmethacrylamide.

Preferred components B2 are vinyl (meth)acrylate, tetraethylene glycoldi(meth)acrylate, dipropylene glycol di(meth)acrylate, hexane-1,6-dioldi(meth)acrylate, neopentyl glycol propoxylate di(meth)acrylate,tripropylene glycol di(meth)acrylate, bisphenol A ethoxylated di(meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycoldi(meth)acrylate, neopentyl glycol di(meth)acrylate, hexamethyleneglycol di(meth)acrylate, bisphenol A di(meth)acrylate and4,4′-bis(2-(meth)acryloyloxyethoxy)diphenylpropane.

Preferred components B3 are ethoxylated trimethylolpropanetri(meth)acrylate, propoxylated glycerol tri(meth)acrylate,pentaerythritol tri(meth)acrylate, trimethylolpropaneethoxytri(meth)acrylate, trimethylolpropane tri(meth)acrylate,alkoxylated tri(meth)acrylate and tris(2-(meth)acryloylethyl)isocyanurate.

Trimerization Catalyst C

The trimerization catalyst C may be mixed from one catalyst type ordifferent catalyst types, but contains at least one catalyst that bringsabout the trimerization of isocyanate groups to isocyanurates oriminooxadiazinediones.

Suitable catalysts for the process of the invention are, for example,simple tertiary amines, for example triethylamine, tributylamine,N,N-dimethylaniline, N-ethylpiperidine or N,N′-dimethylpiperazine.Suitable catalysts are also the tertiary hydroxyalkylamines described inGB 2 221 465, for example triethanolamine, N-methyldiethanolamine,dimethylethanolamine, N-isopropyldiethanolamine and1-(2-hydroxyethyl)pyrrolidine, or the catalyst systems known from GB 2222 161 that consist of mixtures of tertiary bicyclic amines, forexample DBU, with simple aliphatic alcohols of low molecular weight.

Likewise suitable as trimerization catalysts for the process of theinvention are a multitude of different metal compounds. Suitableexamples are the octoates and naphthenates of manganese, iron, cobalt,nickel, copper, zinc, zirconium, cerium or lead or mixtures thereof withacetates of lithium, sodium, potassium, calcium or barium that aredescribed as catalysts in DE-A 3 240 613, the sodium and potassium saltsof linear or branched alkanecarboxylic acids having up to 10 carbonatoms that are known from DE-A 3 219 608, for example of propionic acid,butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid,pelargonic acid, capric acid and undecylenoic acid, the alkali metal oralkaline earth metal salts of aliphatic, cycloaliphatic or aromaticmono- and polycarboxylic acids having 2 to 20 carbon atoms that areknown from EP-A 0 100 129, for example sodium or potassium benzoate, thealkali metal phenoxides known from GB-A 1 391 066 and GB-A 1 386 399,for example sodium or potassium phenoxide, the alkali metal and alkalineearth metal oxides, hydroxides, carbonates, alkoxides and phenoxidesknown from GB 809 809, alkali metal salts of enolizable compounds andmetal salts of weak aliphatic or cycloaliphatic carboxylic acids, forexample sodium methoxide, sodium acetate, potassium acetate, sodiumacetoacetate, lead 2-ethylhexanoate and lead naphthenate, the basicalkali metal compounds complexed with crown ethers or polyether alcoholsthat are known from EP-A 0 056 158 and EP-A 0 056 159, for examplecomplexed sodium or potassium carboxylates, the pyrrolidinone-potassiumsalt known from EP-A 0 033 581, the mono- or polynuclear complex oftitanium, zirconium and/or hafnium known from application EP 13196508.9,for example zirconium tetra-n-butoxide, zirconium tetra-2-ethylhexanoateand zirconium tetra-2-ethylhexoxide, and tin compounds of the typedescribed in European Polymer Journal, vol. 16, 147-148 (1979), forexample dibutyltin dichloride, diphenyltin dichloride,triphenylstannanol, tributyltin acetate, tributyltin oxide, tindioctoate, dibutyl(dimethoxy)stannane and tributyltin imidazolate.

Further trimerization catalysts suitable for the process of theinvention are, for example, the quaternary ammonium hydroxides knownfrom DE-A 1 667 309, EP-A 0 013 880 and EP-A 0 047 452, for exampletetraethylammonium hydroxide, trimethylbenzylammonium hydroxide,N,N-dimethyl-N-dodecyl-N-(2-hydroxyethyl)ammonium hydroxide,N-(2-hydroxyethyl)-N,N-dimethyl-N-(2,2′-dihydroxymethylbutyl)ammoniumhydroxide and 1-(2-hydroxyethyl)-1,4-diazabicyclo[2.2.2]octane hydroxide(monoadduct of ethylene oxide and water with1,4-diazabicyclo[2.2.2]octane), the quaternary hydroxyalkylammoniumhydroxides known from EP-A 37 65 or EP-A 10 589, for exampleN,N,N-trimethyl-N-(2-hydroxyethyl)ammonium hydroxide, thetrialkylhydroxylalkylammonium carboxylates that are known from DE-A2631733, EP-A 0 671 426, EP-A 1 599 526 and U.S. Pat. No. 4,789,705, forexample N,N,N-trimethyl-N-2-hydroxypropylammonium p-tert-butylbenzoateand N,N,N-trimethyl-N-2-hydroxypropylammonium 2-ethylhexanoate, thequaternary benzylammonium carboxylates known from EP-A 1 229 016, suchas N-benzyl-N,N-dimethyl-N-ethylammonium pivalate,N-benzyl-N,N-dimethyl-N-ethylammonium 2-ethylhexanoate,N-benzyl-N,N,N-tributylammonium 2-ethylhexanoate,N,N-dimethyl-N-ethyl-N-(4-methoxybenzyl)ammonium 2-ethylhexanoate orN,N,N-tributyl-N-(4-methoxybenzyl)ammonium pivalate, thetetrasubstituted ammonium α-hydroxycarboxylates known from WO2005/087828, for example tetramethylammonium lactate, the quaternaryammonium or phosphonium fluorides known from EP-A 0 339 396, EP-A 0 379914 and EP-A 0 443 167, for example N-methyl-N,N,N-trialkylammoniumfluorides with C8-C10-alkyl radicals, N,N,N,N-tetra-n-butylammoniumfluoride, N,N,N-trimethyl-N-benzylammonium fluoride,tetramethylphosphonium fluoride, tetraethylphosphonium fluoride ortetra-n-butylphosphonium fluoride, the quaternary ammonium andphosphonium polyfluorides known from EP-A 0 798 299, EP-A 0 896 009 andEP-A 0 962 455, for example benzyltrimethylammonium hydrogenpolyfluoride, the tetraalkylammonium alkylcarbonates which are knownfrom EP-A 0 668 271 and are obtainable by reaction of tertiary amineswith dialkyl carbonates, or betaine-structured quaternary ammonioalkylcarbonates, the quaternary ammonium hydrogencarbonates known from WO1999/023128, such as choline bicarbonate, the quaternary ammonium saltswhich are known from EP 0 102 482 and are obtainable from tertiaryamines and alkylating esters of phosphorus acids, examples of such saltsbeing reaction products of triethylamine, DABCO or N-methylmorpholinewith dimethyl methanephosphonate, or the tetrasubstituted ammonium saltsof lactams that are known from WO 2013/167404, for exampletrioctylammonium caprolactamate or dodecyltrimethylammoniumcaprolactamate.

Further trimerization catalysts C suitable for the process of theinvention can be found, for example, in J. H. Saunders and K. C. Frisch,Polyurethanes Chemistry and Technology, p. 94 ff. (1962) and theliterature cited therein.

Particular preference is given to carboxylates and phenoxides with metalor ammonium ions as counterion. Suitable carboxylates are the anions ofall aliphatic or cycloaliphatic carboxylic acids, preferably those withmono- or polycarboxylic acids having 1 to 20 carbon atoms. Suitablemetal ions are derived from alkali metals or alkaline earth metals,manganese, iron, cobalt, nickel, copper, zinc, zirconium, cerium, tin,titanium, hafnium or lead. Preferred alkali metals are lithium, sodiumand potassium, more preferably sodium and potassium. Preferred alkalineearth metals are magnesium, calcium, strontium and barium.

Very particular preference is given to the octoate and naphthenatecatalysts described in DE-A 3 240 613, these being octoates andnaphthenates of manganese, iron, cobalt, nickel, copper, zinc,zirconium, cerium or lead, or mixtures thereof with acetates of lithium,sodium, potassium, calcium or barium.

Very particular preference is likewise given to sodium benzoate orpotassium benzoate, to the alkali metal phenoxides known from GB-A 1 391066 and GB-A 1 386 399, for example sodium phenoxide or potassiumphenoxide, and to the alkali metal and alkaline earth metal oxides,hydroxides, carbonates, alkoxides and phenoxides that are known from GB809 809.

The trimerization catalyst C preferably contains a polyether. This isespecially preferred when the catalyst contains metal ions. Preferredpolyethers are selected from the group consisting of crown ethers,diethylene glycol, polyethylene glycols and polypropylene glycols. Ithas been found to be of particular practical relevance in the process ofthe invention to use a trimerization catalyst B containing, aspolyether, a polyethylene glycol or a crown ether, more preferably18-crown-6 or 15-crown-5. Preferably, the trimerization catalyst Bcomprises a polyethylene glycol having a number-average molecular weightof 100 to 1000 g/mol, preferably 300 g/mol to 500 g/mol and especially350 g/mol to 450 g/mol.

Very particular preference is given to the combination of theabove-described carboxylates and phenoxides of alkali metals or alkalineearth metals with a polyether.

Component D

Component D is a compound having at least one isocyanate-reactive groupas defined further up in this application and at least one ethylenicdouble bond in one molecule. The isocyanate-reactive group of componentD may also be a uretdione group. Ethylenic double bonds are preferablythose that are crosslinkable with other ethylenic double bonds by afree-radical reaction mechanism. Corresponding activated double bondsare defined in detail further up in this application for component B.

Preferred components D are alkoxyalkyl (meth)acrylates having 2 to 12carbon atoms in the hydroxyalkyl radical. Particular preference is givento 2-hydroxyethyl acrylate, the isomer mixture formed on addition ofpropylene oxide onto acrylic acid, or 4-hydroxybutyl acrylate.

Component E

Component E is a compound having both at least one isocyanate group andat least one ethylenic double bond in one molecule. It canadvantageously be obtained by crosslinking a component D described inthe preceding paragraph with a monomeric or oligomeric polyisocyanate asdescribed further up in this application. This crosslinking is effectedby the reaction of the isocyanate-reactive groups, in this caseespecially a hydroxyl, amino or thiol group, and an isocyanate group ofthe polyisocyanate. This is preferably catalyzed by a component G, whichis described further down in this application. But any other suitablecatalyst known to those skilled in the art is also conceivable. It isalso possible to dispense with a catalyst entirely.

The isocyanate group of component E may also be in reversibly blockedform. The reversible blocking of isocyanate groups is preferablyeffected with blocking agents that are free of elimination products.

In a further preferred embodiment, the free-radically crosslinkablestructural material contains blocked or unblocked NCO groups. When theNCO groups are blocked, the process of the invention further includesthe step of deblocking these NCO groups. After they have been deblocked,they are thus available for further reactions.

The blocking agent is chosen such that, on heating in the process of theinvention, the NCO groups are at least partly deblocked. Examples ofblocking agents are alcohols, lactams, oximes, malonic esters, alkylacetoacetates, triazoles, phenols, imidazoles, pyrazoles and amines, forexample butanone oxime, diisopropylamine, 1,2,4-triazole,dimethyl-1,2,4-triazole, imidazole, diethyl malonate, ethylacetoacetate, acetone oxime, 3,5-dimethylpyrazole, ε-caprolactam,N-methyl-, N-ethyl-, N-(iso)propyl-, N-n-butyl-, N-isobutyl-,N-tert-butylbenzylamine or 1,1-dimethylbenzylamine,N-alkyl-N-1,1-dimethylmethylphenylamine, adducts of benzylamine ontocompounds having activated double bonds, such as malonic esters,N,N-dimethylaminopropylbenzylamine and other optionally substitutedbenzylamines containing tertiary amino groups and or dibenzylamine orany desired mixtures of these blocking agents.

Particular preference is given to combinations in which a hexamethylenediisocyanate- or pentamethylene diisocyanate-based oligomericpolyisocyanate is combined with a component D selected from the groupconsisting of 2-hydroxyethyl acrylate, the isomer mixture formed onaddition of propylene oxide onto acrylic acid, and 4-hydroxybutylacrylate.

Further preferred components E are 2-isocyanatoethyl (meth)acrylate,tris(2-hydroxyethyl) isocyanate tri(meth)acrylate, vinyl isocyanates,allyl isocyanates and 3-isopropenyl-α,α-dimethylbenzyl isocyanate.

Component F

In principle, free-radical polymerization of the ethylenicallyunsaturated compounds present in the reaction mixture can be broughtabout by actinic radiation with a sufficient energy content. This isespecially UV-VIS radiation in the wavelength range between 200 and 500nm. In this case, the polymerizable composition of the invention neednot contain any component F.

But if the use of corresponding radiation is to be dispensed with, thepresence of at least one component F suitable as an initiator for afree-radical polymerization of the ethylenic double bonds present in thepolymerizable composition of the invention is required. This component Fis preferably a radiation-activated initiator.

Preferred radiation-activated initiators F are compounds of theunimolecular type (I) and of the bimolecular type (II). Suitable type(I) systems are aromatic ketone compounds, for example benzophenones incombination with tertiary amines, alkylbenzophenones,4,4′-bis(dimethylamino)benzophenone (Michler's ketone), anthrone andhalogenated benzophenones or mixtures of the recited types. Alsosuitable are type (II) initiators such as benzoin and derivativesthereof, benzil ketals, acylphosphine oxides,2,4,6-trimethylbenzoyldiphenylphosphine oxide, bisacylphosphine oxides,phenylglyoxylic esters, camphorquinone, α-aminoalkylphenones,α,α-dialkoxyacetophenones and α-hydroxyalkylphenones. Specific examplesare Irgacure®500 (a mixture of benzophenone and 1-hydroxycyclohexylphenyl ketone, from Ciba, Lampertheim, Del.), Irgacure®819 DW(phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, from Ciba,Lampertheim, Del.) or Esacure® KIP EM(oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanones], fromLamberti, Aldizzate, Italy) and bis(4-methoxybenzoyl)diethylgermanium.Mixtures of these compounds may also be employed.

It should be ensured that the photoinitiators have a sufficientreactivity toward the radiation source used. A multitude ofphotoinitiators is known on the market. Commercially availablephotoinitiators cover the wavelength range of the entire UV-VISspectrum.

Component G

Component G is a catalyst that catalyzes the crosslinking of anisocyanate group with an isocyanate-reactive group. This preferablygives rise to a urethane group, a thiourethane group or a urea group.

The polymerizable composition preferably contains a component G when acomponent D having at least one isocyanate-reactive group is present.However, the use of a component G is not obligatory in this case either,since the crosslinking of isocyanate groups with isocyanate-reactivegroups can also be accelerated by the trimerization catalysts C used andalso proceeds at sufficient speed even entirely without catalysis whenthe reaction temperature is high enough. It is possible to dispense withthe addition of a component G especially when the crosslinking of theisocyanate groups present in the isocyanate component A is conducted ata temperature of at least 60° C., preferably at least 120° C.

Preferred components G are the typical urethanization catalysts asspecified, for example, in Becker/Braun, Kunststoffhandbuch [PlasticsHandbook] volume 7, Polyurethane [Polyurethanes], section 3.4. Thecatalyst used may especially be a compound selected from the group ofthe tertiary amines, tertiary amine salts, metal salts and metalorganyls, preferably from the group of the tin salts, tin organyls andbismuth organyls.

Component H

According to the invention, the viscosity of the polymerizablecomposition is preferably adjusted by the use of a component B insuitable concentration. These act as reactive diluents and basicallymake it possible to dispense with the use of additional solvents tolower the viscosity of the isocyanate component A.

In particular embodiments, however, it may be desirable to additionallyadd a solvent suitable for isocyanates to the polymerizable compositionof the invention. This may be desirable, for example, when theproportion of component B in the polymerizable composition is to belimited and the aim is a lowering of viscosity unachievable with thislimited proportion of component B. In this case, the polymerizablecomposition of the invention may contain all solvents suitable for thedilution of isocyanates that are known to the person skilled in the art.These are preferably hexane, toluene, xylene, chlorobenzene, ethylacetate, butyl acetate, diethylene glycol dimethyl ether, dipropyleneglycol dimethyl ether, ethylene glycol monomethyl or monoethyl etheracetate, diethylene glycol ethyl and butyl ether acetate, propyleneglycol monomethyl ether acetate, 1-methoxyprop-2-yl acetate,3-methoxy-n-butyl acetate, propylene glycol diacetate, acetone, methylethyl ketone, methyl isobutyl ketone, cyclohexanone, lactones such asβ-propiolactone, γ-butyrolactone, ε-caprolactone andε-methylcaprolactone, but also solvents such as N-methylpyrrolidone andN-methylcaprolactam, 1,2-propylene carbonate, methylene chloride,dimethyl sulfoxide, triethyl phosphate or any desired mixtures of suchsolvents.

Component I

In a preferred embodiment, the polymerizable composition of theinvention additionally comprises at least one additive I selected fromthe group consisting of UV stabilizers, antioxidants, mold releaseagents, water scavengers, slip additives, defoamers, leveling agents,rheology additives, flame retardants and pigments. These auxiliaries andadditives, except for the flame retardants, are typically present in anamount of not more than 20% by weight, preferably not more than 10% byweight and more preferably not more than 3% by weight, based on thepolymerizable composition of the invention. According to the end use,flame retardants may be present in higher amounts of up to a maximum of40% by weight.

Component J

In a particularly preferred embodiment of the present invention, thepolymerizable composition comprises at least one organic filler and/orat least one inorganic filler. Said fillers may be present in any shapeand size known to the person skilled in the art.

Preferred organic fillers are dyes and organic nanoparticles, forexample those based on carbon.

Preferred inorganic fillers are pigments AlOH₃, CaCO₃, silicon dioxide,magnesium carbonate, TiO₂, ZnS, minerals containing silicates, sulfates,carbonates and the like, such as magnesite, baryte, mica, dolomite,kaolin, talc, clay minerals, and carbon black, graphite, boron nitride,glass, basalt, boron, ceramic and silica.

The coating composition of the invention more preferably contains atleast one organic or inorganic pigment.

Use

In a further embodiment, the present invention relates to the use of atleast one component selected from the group consisting of components B,D and E for production of a coating composition having a ratio ofisocyanate groups to isocyanate-reactive groups of at least 2.0:1.0,which contains an isocyanate component A and is polymerizable either byfree-radical polymerization or by crosslinking of isocyanate groups withone another.

Preferably, at least one component B as defined above in thisapplication is additionally used.

All definitions given further up in this application for the coatingcomposition are also applicable to this embodiment. This is especiallytrue of the quantitative ratios of components A, B, D and E and theratio of isocyanate groups to the total amount of theisocyanate-reactive groups in the polymerizable composition.

Process

In a further embodiment, the present invention relates to a process forpreparing a coating, comprising the steps of

-   -   a) providing a coating composition as described further up in        this application;    -   b) applying the coating composition to a surface;    -   c) crosslinking at least some of the ethylenic double bonds        present in said polymerizable composition; and    -   d) crosslinking the isocyanate groups present in said        polymerizable composition;

wherein process step b) is conducted first, then process step c) andfinally process step d).

All other definitions given above with regard to the polymerizablecomposition of the invention are also applicable to the process of theinvention, unless stated otherwise hereinafter.

When the polymerizable composition contains at least one component D, itis preferable that the process of the invention includes a furtherreaction step e) in which the isocyanate-reactive group of component Dis crosslinked with an isocyanate group of the isocyanate component A orof a reaction product of the isocyanate component A. Said process stepe) is preferably conducted after process step c). In most cases,however, it will be effected in parallel to process step e) since boththe crosslinking of isocyanate groups with one another and the reactionof isocyanate groups with isocyanate-reactive groups proceed at similartemperatures.

Processes for producing an adhesive bond comprising the steps of

-   -   a) providing a coating composition as defined further up in this        application;    -   b) applying the coating composition to a surface;    -   c) polymerizing at least some of the ethylenic double bonds        present in said polymerizable composition;    -   d) compressing the at least one coated surface together with a        further surface; and    -   e) crosslinking the reactive isocyanate groups present in said        polymerizable composition and the ethylenic double bonds as yet        unconverted in process step c);    -   wherein process steps c), d) and e) are conducted in any        sequence after process step b).

It is preferable that process step c) is conducted prior to processsteps d) and e).

If not all ethylenic double bonds have yet been polymerized in processstep c), the unconverted double bonds are converted in process step e).

Applying to a Surface

The composition of the invention can be applied by different methodsknown per se. These are preferably spraying, painting, dipping, pouring,flow-coating or coating with the aid of brushes, rolls, nozzles orcoating bars. Particular preference is given to printing technologies,especially screen-printing, valvejet, bubblejet and piezo printing. Thesurface to be coated has to be adequately wetted by the composition ofthe invention. Adequate wettability of a surface is preferably definedin that the contact angle of the liquid on the surface is not more than100°, the contact angle measurement preferably being conducted by meansof a tensiometer by the Wilhelmy method.

Preferably, the surface to be coated consists of a material selectedfrom the group consisting of minerals, metal, rigid plastics, flexibleplastics, textiles, leather, wood, wood derivatives and paper. Mineralsare preferably selected from the group consisting of glass, stone,ceramic materials and concrete. In a particularly preferred embodiment,these materials are already in the form of surfaces modified withcustomary organic or inorganic or hybrid lacquers, primers or waxes.

Crosslinking of the Ethylenic Double Bonds

The ethylenic double bonds present in the polymerizable composition ofthe invention are crosslinked by a free-radical polymerization. Thispolymerization reaction is initiated in accordance with the invention bythe use of radiation suitable for activation of the radiation-activatedinitiator F. In principle, however—irrespective of the presence of aninitiator—the use of sufficiently high-energy radiation as definedfurther up in this application is also sufficient to initiate thefree-radical polymerization in process step c).

It is preferable that process step c) is conducted not more than 120seconds, more preferably not more than 30 seconds, after process stepb).

Crosslinking of the Isocyanate Groups

The “crosslinking” of the isocyanate component A in process step d) is aprocess in which the isocyanate groups present therein react with oneanother or with urethane groups already present to form at least onestructure selected from the group consisting of uretdione, isocyanurate,allophanate, biuret, iminooxadiazinedione and oxadiazinetrionestructures. In this reaction, the isocyanate groups originally presentin the isocyanate component A are consumed. The formation of theaforementioned groups results in combination of the monomeric andoligomeric polyisocyanates present in the isocyanate composition A toform a polymer network.

Since there is a distinct molar excess of isocyanate groups overisocyanate-reactive groups in the polymerizable composition of theinvention, the result of the crosslinking reaction is that at most 20%,preferably at most 10%, more preferably at most 5%, even more preferablyat most 2% and especially at most 1% of the total nitrogen content ofthe isocyanate component A is present in urethane and/or allophanategroups.

In a particularly preferred embodiment of the invention, the curedisocyanate component A, however, is not entirely free of urethane andallophanate groups. Consequently, taking account of the upper limitsdefined in the preceding paragraph, it preferably contains at least 0.1%urethane and/or allophanate groups based on the total nitrogen content.

It is preferable that the crosslinking of the isocyanate groups presentin the polymerizable composition of the invention proceeds predominantlyvia cyclotrimerization of at least 50%, preferably at least 60%, morepreferably at least 70%, especially at least 80% and most preferably 90%of the free isocyanate groups present in the isocyanate component A togive isocyanurate structural units, Thus, in the finished material,corresponding proportions of the nitrogen originally present in theisocyanate component A are bound within isocyanurate structures.However, side reactions, especially those to give uretdione, allophanateand/or iminooxadiazinedione structures, typically occur and can even beused in a controlled manner in order to advantageously affect, forexample, the glass transition temperature (Tg) of the polyisocyanurateplastic obtained. However, the above-defined content of urethane and/orallophanate groups is preferably present in this embodiment too.

The crosslinking of the isocyanate groups is preferably effected attemperatures between 50° C. and 220° C., more preferably between 80° C.and 200° C. and even more preferably between 100° C. and 200° C.

The abovementioned temperatures are maintained in process step d) untilat least 50%, preferably at least 75% and even more preferably at least90% of the free isocyanate groups present in the isocyanate component Aat the start of process step b) have been consumed. The percentage ofisocyanate groups still present can be determined by a comparison of thecontent of isocyanate groups in % by weight in the isocyanate componentA present at the start of process step b) with the content of isocyanategroups in % by weight in the reaction product, for example by theaforementioned comparison of the intensity of the isocyanate band atabout 2270 cm⁻¹ by means of IR spectroscopy.

The exact duration of process step d) naturally depends on the geometryof the workpiece to be created, especially the ratio of surface area andvolume, since the required temperature has to be attained for theminimum time required even in the core of the workpiece being formed.The person skilled in the art is able to determine these parameters bysimple preliminary tests.

In principle, crosslinking of the above mentioned proportions of freeisocyanate groups is achieved when the abovementioned temperatures aremaintained for 1 minute to 4 hours. Particular preference is given to aduration between 1 minute and 15 minutes at temperatures between 180° C.and 220° C. or a duration of 5 minutes to 120 minutes at a temperatureof 120° C.

Polymer

In yet a further embodiment, the present invention relates to a coatingobtainable by the process described above.

A “coating” is preferably characterized in that it has been applied to asubstrate. This substrate is preferably selected from the groupconsisting of wood, plastic, metal, natural rock, concrete, paper andglass. In this respect, the present invention also relates to asubstrate coated with the polymer of the invention. The coating is morepreferably characterized in that the layer thickness is at least 0.005mm and at most 5 mm and preferably has a measurement in at least one ofthe two other dimensions of at least a factor of 10, more preferably100, of the layer thickness. Preferably in both the aforementionedfactors are attained in both further dimensions.

In a further embodiment, the present invention relates to at least onecoating which is compressed between two substrates having been appliedto at least one substrate and is then polymerized and crosslinked andhence acts as an adhesive.

In a particular embodiment, prior to the compression, the at least onecoating between the two substrates, at least one of which has beencoated in accordance with the invention, is prepolymerized by use ofactinic radiation and/or heat with the aim of obtaining a dimensionallystable adhesive coating according to the invention prior to thecompression.

The examples which follow serve only to illustrate the invention. Theyare not intended to limit the scope of protection of the patent claimsin any manner.

EXAMPLES

General Details:

All percentages, unless stated otherwise, are based on percent by weight(% by weight).

The ambient temperature of 23° C. at the time of conduct of theexperiments is referred to as RT (room temperature).

The methods detailed hereinafter for determination of the appropriateparameters were employed for conduction and evaluation of the examplesand are also the methods for determination of the parameters ofrelevance in accordance with the invention in general.

Starting Compounds

Polyisocyanate A: HDI trimer (NCO functionality >3) with an NCO contentof 23.0% by weight from Covestro AG. The viscosity is about 1200 mPa·sat 23° C. (DIN EN ISO 3219/A.3).

Acrylate 1: hexanediol diacrylate (HDDA) was sourced with a purity of99% by weight from abcr GmbH or with a purity of <=100% by weight fromSigma-Aldrich.

Acrylate 2: hydroxypropyl methacrylate (HPMA) was sourced with a purityof 98% by weight from abcr GmbH.

Potassium acetate was sourced with a purity of >99% by weight fromACROS.

Lucirin TPO-L is an ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate fromBASF.

Polyethylene glycol (PEG) 400 was sourced with a purity of >99% byweight from ACROS.

All raw materials except for the catalyst and HPMA were degassed underreduced pressure prior to use.

Preparation of the Catalysts:

Potassium acetate (5.0 g) was stirred in the PEG 400 (95.0 g) at RTuntil all of it had dissolved. In this way, a 5% by weight solution ofpotassium acetate in PEG 400 was obtained and was used as catalystwithout further treatment.

Preparation of the Reaction Mixture

Unless stated otherwise, the reaction mixture was prepared by mixingpolyisocyanate (A1-A2) and the acrylate(s) with an appropriate amount ofcatalyst, initiator and optionally additive at 23° C. in a SpeedmixerDAC 150.1 FVZ from Hauschild at 2750 min⁻¹.

This was then knife-coated onto a glass plate (tin-free side, 250 μm).

In a first crosslinking step, the layer applied was treated by means ofUV curing with a gallium-doped mercury vapor lamp and an undoped mercuryvapor lamp, both operated at 80 W/cm and with a belt speed of 5 m/min.The dose obtained under these conditions is 1400 mJ/cm².

After the first crosslinking step, the plate was placed on its edge andit was observed whether the UV light-treated coating runs or not.

Subsequently, the coating was cured completely. For this purpose, it wasintroduced into an air circulation oven at 180° C. for 15 min.

Test Methods

Run-Off

The coated plate was placed onto a paper towel on its edge for 10 min,and a visual assessment was made as to whether the coating runs. Ifthere is a perceptible change in the coating as a result of the uprightposition (for example formation of a bulge at the lower edge), thecoating is classified as “runs off”.

Acetone Resistance

A small piece of cotton wool is soaked with acetone and placed onto thecoating surface. Every minute, the piece of cotton wool was soaked againwith acetone in order to compensate for the evaporation. For thispurpose, the acetone was added by means of a wash bottle in order thatthe piece of cotton wool is not moved during the contact operation.After 1 min and 5 min, the acetone-soaked piece of cotton wool isremoved, the affected site is dried off and an inspection is madeimmediately in order to anticipate any regeneration. The test area isinspected for changes visually and by touching by hand. Subsequently, anassessment is made as to whether and what changes have occurred in thetest area.

An assessment is made of softening or discoloration of the coatingsurface.

-   -   0 no changes detectable    -   1 swelling ring, hard surface, merely visible alteration/trace        of a change in hue    -   2 swelling ring, slight softening/slight change in hue    -   3 distinct softening (possible slight blistering)/moderate        change in hue    -   4 significant softening (possibly significant blistering), can        be scratched through down to the substrate/significant change in        hue    -   5 coating completely destroyed without outside action/very        significant change in hue

Hardness

Hardness is the mechanical resistance of a body to the penetration ofanother body. It is the quotient of measured indentation force and thecontact area of the indentation body on penetration into the surface.The contact area is calculated with the known geometry of thepenetration body and the measured indentation depth.

In the case of the instrumented indentation test (Martens hardness),indentation force and indentation depth are measured during thedeformation, taking account of the elastic and plastic deformation. Apyramidal indentation body (Vickers tip) presses into the coating withrising test force.

Indentation force, indentation depth and indentation body geometry areused to calculate a Martens hardness value (HM).

Hardness was determined by means of a Fischerscope H100C in accordancewith DIN EN ISO 14577-1.

The samples are conditioned under standard climatic conditions at 23° C.and 50% rel. humidity for at least 16 h and then analyzed. Choice ofmaximum indentation force either the same for all samples within thetest series or individual assessment and adjustment for each sample. Theadjustment criterion here is the Buckle rule, according to which themaximum indentation force is adjusted such that the penetration depthattained is not more than 10% of the coating thickness.

The measurement result reported in table 1 is the Martens hardness HM(F) in N/mm² as an average from 5 measurements.

Visual Assessment

After complete curing, the film was visually assessed and brieflydescribed.

Working Examples:

The amounts of polyisocyanate, acrylate, catalyst solution specified intable 1 were treated according to the abovementioned production methodfor reaction mixtures.

The reaction mixture was coated with a coating bar in a thickness of 250μm onto the tin-free side of a glass plate and then UV-treated with agallium-doped mercury vapor lamp and an undoped mercury vapor lamp.Subsequently, the samples were cured in an air circulation oven at 180°C. for 15 min.

TABLE 1 Compositions and material properties of working examples 1-10Results Catalyst + initiator Martens Resin composition Amount ofhardness HM (F) Acetone resistance Amount of Amount of Amount of Amountof Lucirin [N/mm²] 1 min/5 min Visual observation Isocyanate A Acrylate1 Acrylate 2 Cat. K1 TPOL-L After After After Runoff Appearance Ex. [g][g] [g] [g] [g] curing exposure curing after exposure after curing B150.0 0.5 9.5 2.0 0.3 133 3/3 0/0 no homogeneous layer B2 50.0 0.3757.125 2.0 0.3 126 4/4 0/0 no homogeneous layer B3 50.0 0.25 4.75 2.0 0.3133 5/5 0/0 no homogeneous layer B4 50.0 0.375 9.5 2.0 0.3 130 3-4/4 0/0 no homogeneous layer B5 50.0 0.25 9.5 2.0 0.3 134 3-4/4   0/0-1 nohomogeneous layer B6 50.0 0.0 0 2.0 0.3 135 5/5 0/0 obvious homogeneouslayer

All examples where the number is preceded by a B are inventive. Allexamples where the number is preceded by a V are comparative examplesand noninventive. Comparative example 1 is prophetic.

All examples show a high Martens hardness HM (F) after complete curing.

Examples B1 to B5 show that runoff-free films are obtained afterradiative curing and homogeneous clear hard films after complete curing.

Comparative example V1 shows that the straight isocyanate afterradiative curing does not form a runoff-free layer.

1.-15. (canceled)
 16. A coating composition having a ratio of isocyanategroups to isocyanate-reactive groups of at least 2.0:1.0, comprising thefollowing components: a) an isocyanate component A; b) at least onetrimerization catalyst C; and c) at least one component selected fromthe group consisting of components B, D and E, where component B has atleast one ethylenic double bond but no isocyanate-reactive group;component D has at least one isocyanate-reactive group and at least oneethylenic double bond in one molecule; and component E has both at leastone isocyanate group and at least one ethylenic double bond in onemolecule.
 17. The composition as claimed in claim 16, containing atleast one component D or E.
 18. The composition as claimed in claim 16,containing at least one component B.
 19. The composition as claimed inclaim 16, wherein the molar ratio of isocyanate groups toisocyanate-reactive groups in the polymerizable composition is at least4.0:1.0.
 20. The composition as claimed in claim 16, additionallycontaining a component F suitable as a radiation-activated initiator fora free-radical polymerization of the ethylenic double bonds present inthe polymerizable composition of the invention.
 21. The composition asclaimed in claim 16, wherein the proportion of components B, D and E ischosen such that the coating, after free-radical polymerization of theethylenic double bonds present therein, does not run on a verticalsurface.
 22. The use of at least one component selected from the groupconsisting of components B, D and E for production of a coatingcomposition having a ratio of isocyanate groups to isocyanate-reactivegroups of at least 2.0:1.0, which contains an isocyanate component A andis polymerizable either by free-radical polymerization or bycrosslinking of isocyanate groups with one another.
 23. A process forproducing a coating, comprising the steps of a) providing a coatingcomposition as defined in claim 16; b) applying the coating compositionto a surface; c) crosslinking at least some of the ethylenic doublebonds present in said polymerizable composition; and d) crosslinking theisocyanate groups present in said polymerizable composition; whereinprocess step b) is conducted first, then process step c) and finallyprocess step d).
 24. The process as claimed in claim 23, wherein thepolymerizable composition comprises at least one component D and theprocess comprises a further process step d) in which theisocyanate-reactive group of component D is crosslinked with anisocyanate group of the isocyanate component A or of a reaction productof the isocyanate component A.
 25. The process as claimed in claim 23,wherein, in process step d), at least 50% of the free isocyanate groupspresent in isocyanate component A are converted to isocyanuratestructural units.
 26. The process as claimed in claim 23, whereinprocess steps b) and c) are conducted within an interval of not morethan 120 seconds.
 27. A coating obtainable by the process as claimed inclaim
 23. 28. A process for producing an adhesive bond, comprising thesteps of a) providing a coating composition as defined in claim 16; b)applying the coating composition to a surface; c) polymerizing at leastsome of the ethylenic double bonds present in said polymerizablecomposition; d) compressing the at least one coated surface togetherwith a further surface; and e) crosslinking the reactive isocyanategroups present in said polymerizable composition and the ethylenicdouble bonds as yet unconverted in process step c); wherein processsteps c), d) and e) are conducted in any sequence after process step b).29. A coated product obtainable by the process as claimed in claim 23.30. A bonded product obtainable by the process as claimed in claim 28.